This invention relates to a transport conveyor, and more particularly to a sensorless transport conveyor which can be operated so as to selectively stop operation of the conveyor when the conveyor is not being used to transport a load.
Conventional conveyors for transporting individual loads are broadly categorized as either "accumulating" conveyors or "non-accumulating" transport conveyors. Both types of conveyors are typically divided into a series of adjacent conveyor zones, and a motor and drive arrangement is provided for each zone so as to impart rotation to the part of the conveyor which supports the load and transports the load on the conveyor zone, such as a series of conveyor rollers.
Accumulating conveyors are used when it is necessary to keep track of the progress of the individual packages being transported by the conveyor. Each zone of an accumulating conveyor typically includes a sensor at the downstream end for detecting when a load is present at the downstream end of the zone and for providing an input to the downstream and upstream conveyor zones. The motor control of the downstream conveyor zone is responsive to the input so as to operate the downstream zone in a desired manner, i.e. either to operate the zone to advance the load thereon or to accumulate the load on the zone by stopping operation of the zone. The motor control of the upstream conveyor is responsive to the input so as to operate the upstream zone to advance a load on to the conveyor zone downstream therefrom. The sensor input detects when a load is transferred from one zone to another, and can thus be used to stop operation of a zone if the zone is not supporting a load and to resume operation as a load approaches or is transferred to the zone.
Non-accumulating conveyors, also known as transport conveyors, typically include very simple controls and are generally either in an on state in which all zones of the transport conveyor are in operation or an off state in which operation of all zones of the transport conveyor is stopped.
The disadvantage of conventional transport conveyors is that, during operation, all zones of the conveyor are typically in operation even though a large proportion of the conveyor is not transporting a load at any given time. In other words, each zone operates continuously even though the zone may not be in the process of transporting a load. This results in a waste of energy and generation of unnecessary noise in the vicinity of the conveyor. Further, all moving parts of the conveyor are continuously being subjected to mechanical wear.
While it is possible to control operation of a transport conveyor by providing a sensor to control operation of the motor such that the zone is only operable when it is transporting a load, adding a sensor to each zone results in additional cost and creates the need for a communication system for transmitting information throughout the length of the conveyor regarding the full or empty state of each zone to the adjacent zones.
It is an object of the present invention to provide a transport conveyor which eliminates the need for an external sensor and which functions to operate each zone only when necessary to transport a load on the zone. It is a further object of the invention to provide such a conveyor which utilizes a conventional drive system for operating a conveyor zone. A further object of the invention is to provide such a conveyor which is relatively simple in its components and operation and which eliminates the cost associated with an external sensor. A still further object of the invention is to provide such a conveyor which takes advantage of available technology in order to provide selective operation of conveyor zones.
In accordance with one aspect of the invention, a conveyor arrangement for transporting a load, and which defines an upstream end and a downstream end, includes a rotatable conveying member and a motor drivingly interconnected with the conveying member and including a rotatable output member. The conveyor arrangement is constructed and arranged such that advancement of a load thereon upstream of the conveying member results in rotation of the conveying member and thereby rotation of the rotatable output member of the motor. A control arrangement is interconnected with the motor for initiating operation of the motor in response to rotation of the rotatable motor output member and for maintaining operation of the motor for a period of time sufficient to enable a load on the conveyor assembly to pass downstream of the rotatable conveying member. The control arrangement is operable to thereafter stop operation of the motor to stop rotation of the rotatable conveying member. The rotatable conveying member may be in the form of a drive roller with which the motor output member is rotatably interconnected, and the conveyor arrangement may be in the form of a series of driven rollers including an upstream driven roller and a downstream driven roller. A drive arrangement interconnects adjacent driven rollers for driving the driven rollers in response to rotation of the drive roller. The drive arrangement is operable to transfer rotation of the upstream driven roller to the drive roller upon advancement of a load onto the upstream driven roller, for initiating operation of the motor. The control arrangement includes at least one sensor for detecting rotation of the rotatable motor output member and for providing an input in response thereto, and a motor control for operating the motor in response to the sensor input. In a preferred form, the motor may be a brushless DC motor and the sensor may be a Hall Effect sensor. The motor control is preferably operable so as to operate the motor for a predetermined time period after initiation of motor operation in response to the sensor input, sufficient to allow the load to be discharged from the conveyor arrangement. The motor control may be operable to allow the motor to coast subsequent to expiration of the predetermined time period. While the motor is coasting, subsequent advancement of a load onto the conveyor arrangement upstream of the conveying member is detected by the at least one sensor to provide a subsequent sensor input to the motor control to re-initiate operation of the motor for the predetermined time period. The motor control may also include a dynamic brake control to stop rotation of the motor and thereby rotation of the rotatable output member. The motor control is preferably responsive to a stop input to operate the brake so as to positively stop operation of the motor. The stop input may be provided from a stop input line interconnected with the motor control and responsive to a condition external of the conveyor arrangement for providing the stop input to the motor control.
In accordance with another aspect of the invention, a conveyor arrangement for transporting a load, and defining an upstream end and a downstream end, includes a rotatable conveying member and a motor drivingly engaged with the rotatable conveying member through a rotatable motor output member. A control arrangement is interconnected with the motor for controlling operation of the motor. The conveyor arrangement is constructed and arranged to impart rotation to the rotatable conveying member as a load is advanced in a downstream direction toward the conveying member and to thereby impart rotation to the rotatable motor output member. The control arrangement is operable to operate the motor upon rotation of the rotatable output member for a period of time sufficient to enable the load to pass downstream of the rotatable conveying member, and to thereafter stop operation of the motor to cut off the supply of power to the rotatable motor output member.
In accordance with yet another aspect of the invention, a transport conveyor assembly, which extends between an upstream end and a downstream end, includes a series of rotatable conveyor rollers, a motor including a rotatable output member drivingly interconnected with a drive conveyor roller for imparting rotation thereto in response to operation of the motor, and a drive arrangement interconnecting the drive conveyor roller with the remainder of the conveyor rollers, which are driven rollers, so as to impart rotation thereto in response to rotation of the drive conveyor roller. Advancement of a load onto the upstream end of the conveyor assembly engages the upstream driven roller, which is operable to impart rotation to the drive roller through the drive arrangement. This rotation of the driven roller is transferred to the rotatable motor output member. A controller is interconnected with the motor and is operable to initiate operation of the motor in response to rotation of the rotatable motor output member. The controller is also operable to maintain operation of the motor for a time sufficient to enable the load to pass from the downstream end of the conveyor assembly, and to thereafter stop operation of the motor after the load has passed from the downstream end of the conveyor assembly. In this manner, the motor stops the supply of power to the rotatable motor output member and thereby to the drive conveyor roller and the driven conveyor rollers interconnected therewith through the drive arrangement.
The invention also contemplates a method of operating a conveyor assembly to advance a load thereon, substantially in accordance with the foregoing summary.